69 



The condition of the Hessian fly in these three plats, at the time of 

 harvest, Jnly 10, 1888, may be inferred from the result of examinations 

 made on this date. 



Empty flaxseeds „ 15 



Containing healthy pupae or parasites 69 



Larvae 16 



Total 100 



August 3, the state of the insect in these same plats was as follows : 



Empty flaxseeds 53 



Containing liealthy pupae and parasites 47 



Total 100 



The condition of the insect on September 1, as shown by examination 

 of the stubble, is indicated below : 



Empty flaxseeds 55 



Healthy flaxseeds 28 



Parasitized flaxseeds 17 



Total 100 



Notwithstanding the percent of healthy puparia passing the summer 

 was small, there is little probability that many adult flies emerged. 

 A plat of the same dimensions was sown July 16, along one side of the 

 first three sown the previous fall, the plants of this last sowing coming 

 up ten days later. This plat was closely watched. After July 17 only 

 an occasional larva was found. By August 4 plants had been de- 

 stroyed by the combined influences of chinch bugs and dry weather, 

 but a second plat has been sown adjoining, and the plants of this ap- 

 peared above ground on August 6. On September 4, 200 plants were 

 examined and but two larvae were found thereon. A second examina- 

 tion of the same number of plants from this plat, on September 15, re- 

 vealed a small number of young larvas. A third examination* of this 

 plat on October 6 showed about 1 per cent of the plants to be infested. 

 Stubble from the three original plats, kept in breeding cages, out of doors, 

 did not give adults until the 17th of September, although it is quite 

 probable that some few were abroad before that date. It will be seen, 

 however, that no great number could have emerged from the stubble, 

 and the increase in the number of empty flaxseeds between July 10 and 

 September lis doubtless to be attributed to parasites. This appears all 

 the more probable, as I have repeatedly observed these parasites 

 during July and August emerge in breeding cages, and at once begin 

 to oviposit in flaxseed in the stubble from which they had themselves 

 emerged. The percentage of healthy puparia reaching September in 

 safety, however, was probably unusally small, as experiments on the 

 same ground the following year did not suffer near so much from either 

 fall or spring attacks. Another feature of these experiments is, that 

 it strongly indicates that the larger per cent of the parasites emerge 

 prior to the 1st of August. Indeed, stubble from the entire length of 



